have to用法

比如 you have to eat that, don't you ?
你不得不吃那个 不是么？

you have seen that haven't you ?
这个是完成时

具体要看have在句子中充当的是什么。。

have to时态多样eg.had to /did not have to /will have to/do not have to,etc. 反意问句把它当作实义动词eg.He has to go home,does not he?

have to 就是肯定的用法，所以反意疑问是否定的